Malware detection coming in Snow Leopard?

We usually look at news updates and blog posts from antivirus vendor Intego with a bit of a gimlet eye, since the company has been known to spread a little bit of that good old FUD when it comes to the everyday risk of malware faced by most Mac users (that is to say, pretty much none). Today, however, the Intego blog pointed out an unheralded feature of the forthcoming Mac OS X 10.6 Snow Leopard update: some basic malware checking built into the operating system, reported by users of the beta version.

As the post notes (and sites such as The Register and ZDnet corroborate), when a problematic DMG is downloaded or mounted -- containing one of two known malware components -- the Finder throws the alert pictured above, warning the user not to install the software in question and to throw away the disk image. While this is a nice touch for the two security risks in question, The Register notes that the filter appears to only catch files downloaded through some of the more common apps (Mail.app, Entourage, Safari, Firefox and iChat among them) but not files copied over from removable media. It doesn't cover the wider gamut of threats out there, nor would it detect or block Windows malware that a Mac user could unwittingly transmit; for all of those scenarios, a true AV app (paid or free) is what the doctor ordered.